Process control systems typically include various components for controlling various process parameters. For example, a fluid process control system may include a plurality of control valves for controlling flow rate, temperature, and/or pressure of a fluid flowing through the system. The end product is dependent on the accuracy of the control of these parameters, which is, in turn, dependent on the geometry and characteristics of the control valves. Control valves are, for example, specifically designed and selected to provide for particular flow capacities and pressure changes. When these characteristics are compromised, the quality of the end product may be affected.
A control valve typically includes components such as a valve body, a valve trim assembly (e.g., a flow control member, a valve stem, a valve seat), and an actuator configured to operably position the flow control member within the valve body. In some cases, it may be desirable (e.g., for cost reasons) to manufacture some of these components, for example a valve trim component of the valve trim assembly, from two or more different materials. However, the valve trim component, by virtue of being made from different materials (which in turn have different thermal expansion coefficients), will have different portions having different thermal expansion coefficients, thereby producing differential expansion between the different portions of the valve trim component when the control valve is used at different temperatures (particularly at elevated temperatures). Such differential thermal expansion may undesirably compromise the characteristics of the control valve, thereby affecting the quality of the end product. Worse yet, differential thermal expansion may eventually cause the valve trim component to fail.